msem-instigator

Counter target spell if it wasn't cast from a player's hand.

Dead Man's Hand enters tapped.
{T}, Sacrifice Dead Man's Hand, two permanents with mana value 1, and two permanents with mana value 8: Target player loses the game.

Dead-Set Duo can't block.
Whenever Dead-Set Duo deals combat damage to a player, you may pay {B} and sacrifice it. If you do, they discard two cards.

Engorge (As this enters, mill three cards, then exile a card from among the milled cards.)
Deadland Mongrel gets +1/+1 if it engorged a creature card with power 3 or greater.

Deadwood Grove enters tapped.
{T}: Add {B} or {G}.
{1}{B}{G}: Until end of turn, Deadwood Grove becomes a 2/3 black and green Horror creature with with deathtouch and “Whenever this creature attacks or blocks, torment yourself.” It's still a land. (To torment yourself, lose 3 life unless you discard a card or sacrifice a nonland permanent.)

When Death Pits Trophy enters, target opponent discards a card.
Equipped creature gets +1/+1.
Equip {1}

Choose a nonlegendary, nonland card name. Target opponent reveals their hand and discards a card with that name.
Agonize (You may cast this card from your graveyard by putting a -1/-1 counter on a creature you control in addition to paying its other costs. Then exile this card.)

Deathtouch
{3}{G}: Deathcoil Cobra gains indestructible until end of turn.

Whenever another creature you control dies, put a +1/+1 counter on Deathfeeder.
Sacrifice Deathfeeder: Target creature gets +X/+X until end of turn, where X is Deathfeeder's power.

Enchant creature
Enchanted creature has winnow. (Damage dealt to it also causes its controller to lose that much life.)

{T}: Add {C}.
{T}, Exile two cards from your graveyard: Add {W} or {B}.

Decayed Bedchamber enters tapped.
When Decayed Bedchamber enters, look at the top card of your library. You may put it into your graveyard.
{T}: Add {B} or {G}.

Target creature gets +2/+2 until end of turn. You may remove a -1/-1 counter from it.

Whenever another creature you control enters, you may change Declan, Wayward Squire's base power and toughness to that creature's power and toughness until end of turn.

Menace (This creature can't be blocked except by two or more creatures.)

{T}, Sacrifice Decrepit Crags: Search your library for a Swamp or Mountain card and put it onto the battlefield tapped, then shuffle.

Target creature gets +1/+0 and gains first strike until end of turn.
Target creature blocks this turn if able.

Counter target spell with mana value 3 or less. If a spell is countered this way, return it to its owner's hand instead of putting it anywhere else.

Deepdrinker's Domain enters tapped.
{T}: Add {U}.

At the beginning of your upkeep, choose an opponent. That player creates a 3/2 colorless Horror creature token.
{2}: Target opponent gains control of Deepdrinker's Effigy.

Deeplife Cavern enters tapped unless you control a Forest.
{T}: Add {U} or {B}.

{T}: Add {C}.
{3}{R}: Until end of turn, Defect's Precinct becomes a 3/3 creature. It's still a land. It has trample if {G} was spent to activate this ability, has vigilance if {W} was spent, and has hexproof if {U} was spent.

Search your library for a basic land card, reveal it, put it into your hand, then shuffle. Create a 1/1 green Elf creature token.

When Defiant Bristles dies, put a +1/+1 counter on target creature.

This spell can't be countered.
You can't lose the game this turn and your opponents can't win the game this turn. Until end of turn, damage that would reduce your life total to less than 1 reduces it to 1 instead.